The present invention relates in general to combination locks, and more particularly to combination locks especially adapted for use on safe doors and the like operated by a rotatable dial and having an integrally unitary arcuately curved bar-like pivoted fence lever of uniform width throughout terminating in a depending fence forming foot spanning the perimeters of the stack of tumbler wheels and drive cam, and provided with means for resisting surreptitious or unauthorized detection of the combination by manipulation techniques.
Conventional locks of the class known as combination locks usually comprise three tumbler wheels which are loosely journalled in coaxial longitudinally spaced relation for rotation within the lock case on a tubular arbor or tumbler post projecting inwardly of the casing from the front wall of the case. The lock dial, which usually has one hundred peripheral calibration marks thereon, is affixed to a dial spindle which extends through a central bore through the tumbler post and through the front wall of the lock case and the door on which it is mounted, and a disk-like cam is keyed or otherwise fastened to the rearmost end of the dial spindle and is arranged coaxially with and spaced immediately rearwardly from the stack or group of tumbler wheels. The drive pin projects forwardly from the drive cam and has a lost motion connection through a conventional fly with the rearmost tumbler wheel to drive the tumbler wheel circumferentially in selected relation to the drive cam. A similar lost motion connection is provided between each of the successive tumbler wheels so that each of the tumbler wheels may be driven upon selecteed rotation of the drive cam. Each of the tumbler wheels and the drive cam are provided with a peripheral notch or gate at a selected radial position on the drive cam and tumbler wheels.
A fence lever is pivotally connected at one end to a reciprocative bolt slidably supported in the lock case and is provided with a formation at its free end which is designed to ride upon the drive cam periphery. In many of such combination locks, the fence lever has a bar or fence member projecting laterally therefrom in overlying relation with the tumbler peripheries of the tumbler wheels. In other locks especially designed for heavy safe door installations and the like, the fence lever, instead of being a relatively thin lever formed from metal strapping or plate material, is formed as a relatively massive integral unitary curved bar-like fence member whose width corresponds substantially to the axial dimension of the stack of tumbler wheels and driving cam and terminates at its free end in a downwardly extending or depending integral unitary foot formation defining a fence portion which corresponds both to the fence lever nose and the fence member of the alternative form described above. In either case, the position of the fence in relation to the length of the fence lever nose, or the location of the lower fence forming surface of the portion of the foot formation overlying the tumbler peripheries relative to the portion of the lower foot formation surface overlying and engaging the periphery of the driving cam are such that the fence portion confronting the tumbler peripheries is spaced slightly from the tumbler peripheries when the portion riding on the driving cam periphery bears on the ungated portions of the latter.
In such combination locks, when the tumbler wheel gatings are out of registry with the fence or the fence bar portions of the fence lever foot, and the dial is turned to the proper position to dispose the drive cam gating below the fence lever nose or the corresponding portion of the fence lever foot, the latter will drop slightly into the drive cam gate until the fence or the other portions of the foot formation bear upon the tumbler peripheries. The rotation of the dial through small arcs in opposite directions from this position will bring portions of the drive cam gate into contact with the fence lever nose or corresponding portion of the fence lever foot formation. These points at which the fence lever nose or foot contacts these opposite surfaces of the entrance to the drive cam gate are known as left and right contact points of the fence lever and may be detected by coordination of the senses of touch and sight by the person manipulating the dial or by highly accurate measuring instruments. A variation in the relation and "feel" of these contact points or the measured distance between them occurs when one of the tumbler gates is positioned beneath the fence or the corresponding portion of the fence lever foot, which is distinguishable from the relation and "feel" or measure of these contact points when all of the tumbler gatings are out of registry with the fence or fence lever foot.
Various modifications in combination lock structure have heretofore been resorted to in an effort to defeat detection of the lock combination in this manner. Among these is the lock structure disclosed in prior U.S. Pat. Nos. 2,575,674; 2,807,954; and 3,339,383 to Harry C. Miller or to Harry C. Miller and others, wherein various types of guard or shielding mechanisms are mounted on the rear face of the drive cam to normally overlap and close the driving cam gate to form a smooth continuation of the drive cam periphery for supporting the fence lever nose when the drive cam gate is in registry with the fence lever nose. Means are provided to limit angular movement of the dial and dial spindle when the guard or shielding mechanism is moved to a position exposing the drive cam gate to receive the fence lever nose and allow the fence lever to contact the tumbler peripheries, to thereby prevent detection of contact points for the fence lever nose. The present invention, however, is directed to improvement of security against unauthorized detection of the opening combination for combination locks of the type wherein the fence lever nose or corresponding portion of the fence lever continuously engages the periphery of the driving cam except when the driving cam gate registers with the fence lever nose or foot portion, and wherein the incorporation of guard or shielding means to normally close the driving cam gate is unsuitable.
It has been previously proposed in U.S. Pat. Nos. 117,478 and 299,695 to Stockwell to provide eccentric rollers in the fence and fence lever nose portion of a combination lock wherein the fence lever is a relatively thin pivoted plate-like member having a fence formation projecting laterally therefrom, and wherein the fence portion and the fence lever nose portion are each provided with eccentric rollers to continuously engage the peripheries of each of the driving cam and tumbler wheels so that when one exerts pressure on the bolt to which the fence lever is directly connected to continuously strain the fence lever nose and fence portions against the driving cam and tumbler wheel peripheries, one cannot obtain satisfactory "micrometric" readings or measurements from the spindle to reliably detect the combination of the lock. However, these early proposals to improve security of combination locks did not provide the protection against surreptitious detection of the lock combination desired to be achieved in locks of the type to which the safe door combination lock construction of the present invention is directed.
An object of the present invention, therefore, is the provision of combination locks especially adapted for safe doors and the like having a massive fence lever member which is highly resistant to deformation or attack provided as an integral unitary lever with a depending foot formation at the free end thereof opposite the pivoted end of the lever member forming the fence to coact with both the peripheries of the stack of tumbler wheels and the periphery of the driving cam to prevent movement of the bolt to which the fence lever is pivoted to retracted position when the driving cam and tumblers are adjusted to the proper unlocking combination positions and to restrain the bolt against movement from projected, locked position when the tumblers and driving cam are not properly aligned in accordance with the opening combination, and having randomly movable contact means incorporated in the portion of the fence lever foot formation confronting the driving cam periphery to bear on the latter and prevent detection of contact points with the driving cam gate with sufficient accuracy to detect the combination of the lock.
Another object of the present invention is the provision of a combination lock of the type described in the immediately preceeding paragraph, wherein a randomly displaceable contact bar member is incorporated in the foot portion of the fence lever member forming the engagement surface portion of the latter for contact with the peripheries of the tumblers and the driving cam to effect random variations in the interengagement charcteristics of the fence lever and driving cam and tumber wheels and thus resist reliable surreptitious or unauthorized detection of the opening combination for the lock.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.